Microwave sintering of hydroxyapatite ceramics

1994 ◽  
Vol 9 (1) ◽  
pp. 180-187 ◽  
Author(s):  
Yi Fang ◽  
Dinesh K. Agrawal ◽  
Della M. Roy ◽  
Rustum Roy
Keyword(s):  
Grain Size ◽  
Mechanical Strength ◽  
Circular Plate ◽  
Microwave Sintering ◽  
Microwave Oven ◽  
Highly Efficient ◽  
Hydroxyapatite Ceramics ◽  
Conventional Methods ◽  
Time And Energy

Hydroxyapatite ceramics have been fabricated by microwave sintering in a 500 W microwave oven. Circular-plate specimens of various green densities were sintered in the oven at 1200 and 1300 °C, for 5, 10, and 20 min, respectively. Ceramics with density up to 97% of the theoretical were obtained. Density, grain size, microstructure, and strength of the ceramics sintered by microwave and by conventional methods were compared. The results show that microwave sintering of hydroxyapatite is not only highly efficient in saving time and energy, but can also improve the microstructure and thus enhance mechanical strength of the ceramics.

Pertinence of the Grain Size on the Mechanical Strength of Polycrystalline Metals

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
N. A. Zontsika ◽  
A. Abdul-Latif ◽  
S. Ramtani
Keyword(s):  
Grain Size ◽  
Mechanical Strength ◽  
Kinematic Hardening ◽  
Uniaxial Stress ◽  
Isotropic Hardening ◽  
Ultrafine Grained ◽  
Consistent Model ◽  
Micromechanical Approach ◽  
Interaction Law ◽  
Small Deformations

Motivated by the already developed micromechanical approach (Abdul-Latif et al., 2002, “Elasto-Inelastic Self-Consistent Model for Polycrystals,” ASME J. Appl. Mech., 69(3), pp. 309–316.), a new extension is proposed for describing the mechanical strength of ultrafine-grained (ufg) materials whose grain sizes, d, lie in the approximate range of 100 nm < d < 1000 nm as well as for the nanocrystalline (nc) materials characterized by d≤100 nm. In fact, the dislocation kinematics approach is considered for characterizing these materials where grain boundary is taken into account by a thermal diffusion concept. The used model deals with a soft nonincremental inclusion/matrix interaction law. The overall kinematic hardening effect is described naturally by the interaction law. Within the framework of small deformations hypothesis, the elastic part, assumed to be uniform and isotropic, is evaluated at the granular level. The heterogeneous inelastic part of deformation is locally determined. In addition, the intragranular isotropic hardening is modeled based on the interaction between the activated slip systems within the same grain. Affected by the grain size, the mechanical behavior of the ufg as well as the nc materials is fairly well described. This development is validated through several uniaxial stress–strain experimental results of copper and nickel.

The Effect of Microwave Sintering Time to PM Aluminum Alloys

2015 ◽  
Vol 754-755 ◽  
pp. 240-244
Author(s):  
M.N. Derman ◽  
Syaza Nabilla Mohd Suhaimi ◽  
Zuraidawani Che Daud
Keyword(s):  
Microwave Sintering ◽  
Microwave Oven ◽  
Solid Particles ◽  
Binding Reaction ◽  
Aluminium Powder ◽  
Sintering Time ◽  
Conventional Sintering ◽  
Rapid Sintering ◽  
Powder Particles ◽  
Solid Liquid

Microwave sintering is new sintering technology method to produce Al alloys. The advantages of this method because of very short sintering time and less production cost compare to conventional sintering. However, the main problems in microwave sintering are required to be controlled sintering time due to rapid sintering mechanism. Therefore the effect of microwave sintering time to PM Aluminium will be studied. The compacted and sintered aluminium powder is placed in a microwave oven at a different period of 5 minutes, 10 minutes, 15 minutes and 20 minutes. Compression of 150 MPa is applied on aluminium powder to form pellets. Palette is shaped to 1cm in diameter and weighs 1g. SiC is placed together with aluminium samples in the microwave for the purpose of absorbing electromagnetic energy and is converted to heat. Results of different period sintering of aluminium pallet production altered physical properties of each sample. For a rapid sintering time, aluminium pallet does not show any binding reaction between powder particles. Whereas, for long microwave sintering period, solid particles phase change into solid-liquid phase caused by the movement and the formation of bonds between particles. Hence, this will be affecting the mechanical properties of the sample material.

Novel Microstructures in Microwave Sintered Silicon Nitride

1996 ◽  
Vol 430 ◽  
Author(s):  
M. E. Brito ◽  
K. Hirao ◽  
M. Toriyama ◽  
M. Hirota
Keyword(s):  
Grain Size ◽  
Silicon Nitride ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mechanical Performance ◽  
Microwave Sintering ◽  
Preliminary Results ◽  
Nitride Ceramics ◽  
Positive Effect ◽  
Sintered Silicon

AbstractPreliminary results on microwave sintering of seeded silicon nitride show that a well defined bi-modal grain size distribution is attainable in Si3N4-Y2O3-Al2O 3-MgO sintered bodies by microwave sintering at 28 GHz of materials seeded with ß-Si3N4 particles (2 vol. %). A positive effect on the mechanical performance is anticipated for these microstructurally controlled silicon nitride ceramics

Synthesis of Cuprate Ceramic Superconductors by Oxidation of Rapidly Quenched Alloy Precursors

1989 ◽  
Vol 169 ◽  
Author(s):  
J.S. Luo ◽  
D. Michel ◽  
J.‐P. Chevalier
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Liquid State ◽  
Planar Flow ◽  
Ceramic Superconductors ◽  
Planar Flow Casting ◽  
Conventional Methods

AbstractWe have produced various high Tc superconductors by oxidation of rapidly quenched alloy precursors produced by planar flow casting. This method generally leads to reactive oxidized powders and improves homogeneity if there is a solubility domain in the liquid state for the alloy. The grain size distribution is often more uniform than that for specimens prepared by conventional methods from mixtures of constituent oxides and carbonates.

Microwave Sintering Technology for the Production of Metal Oxide Varistors

1990 ◽  
Vol 189 ◽  
Author(s):  
G. McMahon ◽  
A. Pant ◽  
R. Sood ◽  
A. Ahmas ◽  
R.T. Holt
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Metal Oxide ◽  
Leakage Current ◽  
Microwave Sintering ◽  
Identical Composition

ABSTRACTA microwave sintering technology has been developed for the production of metal oxide varistors. The electrical properties (leakage current and non-linearity coefficient) of the microwave sintered devices were found to be comparable to those obtained for conventionally sintered varistors of identical composition. Additionally, the reference voltages were greater (by a factor of two) and the biaxial moduli of rupture were higher for the microwave sintered specimens. These differences have been attributed to the smaller grain size associated with the microwave sintered specimens.

Fabrication of Hydroxyapatite Ceramics by Microwave Processing

1992 ◽  
Vol 269 ◽  
Author(s):  
Dinesh. K. Agrawal ◽  
Y. Fang ◽  
D. M. Roy ◽  
R. Roy
Keyword(s):  
Phase Composition ◽  
Microwave Processing ◽  
Microwave Oven ◽  
Starting Material ◽  
Theoretical Density ◽  
Processing Conditions ◽  
Hydroxyapatite Ceramics

ABSTRACTVarious hydroxyapatite (HAp) ceramics were fabricated by microwave processing. By carefully selecting the starting material and controlling the processing conditions, regular HAp ceramics with density up to 97% of the theoretical density, porous HAp ceramics with porosity up to 76%, and fully densified transparent HAp ceramics were obtained by using a 2.45 GHz, 500W microwave oven. These ceramics were characterized for density, microstructure, strength, and phase composition, and the results were compared with the conventionally processed ceramics.

Surface Dissolution of Hydroxyapatite Prepared by Microwave Sintering

2007 ◽  
Vol 330-332 ◽  
pp. 227-230
Author(s):  
Dong Seok Seo ◽  
Hwan Kim ◽  
Kyu Hong Hwang ◽  
Jong Kook Lee
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Heating Rate ◽  
Microwave Sintering ◽  
Starting Material ◽  
Dissolution Behavior ◽  
Distilled Water ◽  
Sintering Process ◽  
Conventional Sintering ◽  
Boundary Dissolution

The aim of this study was to prepare dense hydroxyapatite (HA) by microwave sintering and to evaluate the dissolution behavior in distilled water. Commercially-obtained HA powders having Ca/P ratio of 1.67 were used as a starting material. The as-received powder of granular type consists of nano-sized particles. Microwave sintering was operated at 1200°C for 5 min with a heating rate of 50°C/min. Microwave sintering process reduced grain size of HA, compared with the case of conventional sintering. During the immersion in distilled water for 3-14 days, grain boundary dissolution occurred and the dissolution extended into the bulk following this path. As a result, particles were separated from the structure leaving micron-scale defects.

Nanostructure Evolution of ZnO in Ultra-fast Microwave Sintering

2011 ◽  
Vol 691 ◽  
pp. 65-71 ◽  
Author(s):  
Rodolfo F. K. Gunnewiek ◽  
Ruth Herta Goldsmith Aliaga Kiminami
Keyword(s):  
Grain Size ◽  
Zinc Oxide ◽  
Grain Growth ◽  
Microwave Sintering ◽  
High Heating Rate ◽  
Heating Rates ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Conventional Sintering ◽  
Holding Temperature

Grain growth is inevitable in the sintering of pure nanopowder zinc oxide. Sintering depend on diffusion kinetics, thus this growth could be controlled by ultra-fast sintering techniques, as microwave sintering. The purpose of this work was to investigate the nanostructural evolution of zinc oxide nanopowder compacts (average grain size of 80 nm) subjected to ultra-rapid microwave sintering at a constant holding temperature of 900°C, applying different heating rates and temperature holding times. Fine dense microstructures were obtained, with controlled grain growth (grain size from 200 to 450nm at high heating rate) when compared to those obtained by conventional sintering (grain size around 1.13µm), which leads to excessively large average final grain sizes.

Sign in / Sign up

Export Citation Format

Share Document